Re: In-the-tank fuel pumps cause death and destruction

Heh heh! Reminds me of the time in a presentation to NASA when I got
reprimanded for referring to an activation switch on a joystick for a
robotic arm to be used on the space shuttle as a "dead man switch" (this
was a few months after the Challenger disaster). (After the meeting, I
very quietly joked to a co-worker, "Hmmm - maybe I should have called it
a "dead *astronaut* switch?", insinuating that the objection was to the
use of the politically incorrect word "man" instead of the generic
"person" or "astronaut".)
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

Hi...
If it isn't to be referred to as a firewall anymore; then
I doubt it's to prevent my believing that a fire is
possible...
Be more inclined to think they don't want me assume
that their firewall would necessarily protect me
from one.
Take care.
Ken

Not only that, but in all modern cars with the epa-mandated evap
collection system, if there is a leak detected by a loss in tank
pressure, an idiot lamp will come on in the dash, letting you know that
something is wrong. Same is true if you drive away from the gas station
without putting your gas cap on tight... after about 35 miles or so, the
ECM will see that as a leak in the system, and an SES lamp will come on.
And you DO get your car checked out when you have an indication that
something is wrong... right?

How many cars have you heard of that have exploded or caught fire from
an in-tank fuel pump? In my case, the answer is zero so I don't lose
much sleep over it.
I'm more worried about an inadvertant air bag deployment than I am about
my gas tank exploding. The former is much more likely than that latter
and I've heard of several occurrences of unintended airbag deployment.
Matt

I'd have no qualms being that engineer, and here's why: Gasoline is
combustible in only a narrow ratio range with air. Bored suburban kids
used to get empty paint cans from the hardware store, put a barbecue
sparker with long leads in the side of the can, use an eyedropper to put
two drops of gasoline in the can, hammer on the lid, stretch the sparker
leads and hit the button to cause a loud noise and a flying can lid.
One drop of gasoline didn't work. Three or more didn't work. TWO drops --
and only two drops -- worked.
The ratio of fuel to air is always much too high (or, if you prefer,
the ratio of air to fuel is always much too low) for these hallucinatory
panoramas of firy death some people (even engineers, amazingly enough)
have been talking about in this thread. That's why they don't happen.
DS

Were you by chance a bored suburban kid, or were you the kid behind the
counter at the hardware store (or both)?

Ouch!!
Forget for the moment that you are technically right. You think you
could convince the management, lawyers, insurance companies, and stock
holders that, statistically over the lifetime of 20 million vehicles,
the perfect conditions resulting in huge publicity and multi-million
dollar lawsuits would never be met - not even one time? You know -
seriously - taking your paint cans and eyedroppers into the conference
room just might do it.
Reminds of the engineer that told me I was over-reacting when I went
ballistic when a 3 foot long flame shot out of a known leaking hydrogen
fitting due to a welder welding above it and showering down sparks - oh
- he had draped the hydorgen equipment with a canvas tarp before he
started "to be safe". He was telling me that the conditions for
hydrogen exploding were so specific that the chances of it happening
were extremely small. The funny thing is that hydrogen in a process
oven not 10 feet from that very spot where the flame shot out had
exploded, blowing the door off of the oven so hard that it moved a 40
ton press a few inches when it struck it. Fortunately, no one was
standing in front of the door at the time. Here's the kicker: That
incident happened - not *AFTER* the 3 foot flame incident, but 3 years
*BEFORE* that - and he still told me I was over-reacting - that an
explosion could never happen.
Saying "Oh - that could never happen - let's go ahead and do it" is how
you end up on the 6 o'clock news. 8^)
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

Well, nearly every occurrence of an airbag deployment that I've heard of
is unintended... most people, unless they intend to commit suicide or
ditch a car and fraudulently claim insurance, do not intend to crash and
trigger the airbags. :)
However, there have been a couple of *unwarranted* airbag deployments
that I've heard of.

Pumping section (gerotor, turbine, or roller vane section as the case
may be for a given design) of the pump is below the commutation section.
Check valve in the fuel line keeping the pump full of fuel after pump
is shut off. There will always be a column of liquid fuel above the
pump commutation level.

See above.

See above. It may be that no single-point of failure will cause a
problem. But, as with any system, you can hypothesize a **combination**
of failures that would creat a problem (cutting the odds) - you'd have
to argue whether or not such a combination of failures was credible.
And statistically, those combinations *will* happen. Don't ask me why
there haven't been real "unexplained" explosions.

Too much heat - fire and vapor lock potential in the modern engine
compartment.
I hear you though. Do a google search on my name and
rec.autos.makers.chrysler and "commutation" and you'll see that I was
asking the same questions of Ford and Chrysler engineers when I was an
engineering manager for fuel pump products as a supplier - you'd be
surprised how many of them never even thought to ask the questions -
it's just the way things were done since before they were hired, so they
never thought about it.
I often said it to them, and I said it in this ng, that if in-tank fuel
pumps had not been invented before now, and I thought of doing it, I, as
an engineer, never would have suggested it in today's legal and
corporate environment - I would have kept my mouth shut for career
protection.
Actually, I seriously doubt that it would be being done now if it had
not had several years of being done with no indication that it was a
real problem. IOW - you could never prove, in theory, to a committe of
lawyers, managers, insurers, and MBA's that there could never be a
scenario that an explosion could not occur from some credible
combination of (1) running the tank out of fuel and (2) a bad in-line
check valve in the lines (allowing the liquid to drain back), and (3)
someone turning the ignition key to "run" and the fuel pump running dry
inside. Oh there will always be those who will have some explanation of
why it could never really explode - but wipe out their knowledge that it
has ever been done before and put them in the parallel universe where it
has not been done before and ask them to be the first person to
volunteer to sit in the first vehicle in which it was ever to be tried
the first time it was cranked up, and see if they will do it. Everyone
has great hindsight knowing that it is in reality apparently safe. But
to know ahead of time for sure...?
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

Having worked in the industry for 7 years, I believe that the primary
driver for designs is intial cost to the mfgr., whether in the form of
parts cost or assembly labor. *IF* it can be determined that making
repairs easier and cheaper will help the mfgr.'s bottom line (i.e., if
the buying public becomes painfully aware of the extra cost of ownership
due to a poor design), then that may influence the design. In
MBA-think, if it hurts the customer or costs the customer money, but the
customer never recognizes that to the point of affecting buying
decisions, then there is no value added in making the design better. No
matter how it's sugar coated, in reality, the term "value-added" means
"it improves our profits". IOW, if it is an improvement (for the
consumer), but doesn't ultimately help the bottom line, then it isn't
"value added" (in MBA-think).
Possibly if it is considered to be a high rate of warranty repair item,
then that might be factored in too. But I believe in this case, the
prime motivator was total initial cost to the mfgr. IMO...
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

What beetle had gravity feed? Every one I ever saw/owned/worked on
needed the fuel pump as the tank was at about the same level as the
carb and roughly 8 feet ahead of it. A front mounted pump pushing the
fuel would have reduced the tendancy for the system to vapour lock,
which my '49 did all too regularly in warm weather (and there was
seldom anything OTHER than warm weather in Zambia) running on the
optimistically 70 something octane regular leaded fuel available in
the early seventies.
Now a Model "T" ford was gravity feed. I believe the model "A" was
too. My 1928 Chevy National had a pump that drew the fuel from the
rear mounted tank by engine vacuum, and then fed it from the #48 juice
can sized pump reservoir to the carb by gravity.
The early Fords would occaisionally run out of gas going up a hill, so
you needed to BACK up steep hills. It also helped that reverse was
geared lower than 1st.

If I recall correctly quite a few with the gas heaters used that
system for the heaters. But I wouldn't doubt but that there's
regional differences & my memory may be cloudy as virtually all
original beetle's in this area have returned to mother nature many
many years ago.

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